Electron discharge device



Nov. 21, 1933. -A. H. DENZLER 1,936,187

ELECTRON DI SCHARGE DEVICE Filed May 25, 1931 FIG. 3

I 42 l I i i 4 I l I w 44 as a/ a2 4 l/VVE/VTDR By AH. DE/VZLER ATTORNEYPatented Nov. 21, 1933 v UNITED STATES ELECTRON DISCHARGE DEVICE ArthurH. Denzler, Union City, N. 1., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York Application May23, 1931. Serial No. 539,445

15 Claims.

This invention relates to electron discharge devices and moreparticularly to such devices in which a diffusible substance is present.

Heretofore considerable difliculty has been experienced in controllingdiffusible material, for

instance, highly emissive substances coated on or combined with a corematerial which is usually heated to initiate the flow of electrons fromthe substance. Usually the emissive substance is coated on a cathode ofa discharge device and cooperates with other electrodes to performvarious functions relating to the amplification or rectification offeeble electrical currents. The electrodes are generally combined in aunitary structure with the electrode supports held in close relationshipby spacers or bridging members usually of insulating material. The closeproximity of the supports for the electrodes and the danger of theemissive material being thrown off the cathode during operation andbeing deposited on the spacers to form a conductive path between thesupports cause irregular functioning of the electrodes and materiallyreduce the operating life of the discharge device.

One object of this invention is to prevent the formation of conductivepaths between electrodes of discharge devices.

In accordance with this invention the electrodes of an electrondischarge device, such as a cathode, a grid and. an anode, are heldrigidly in spaced relation by an insulating member at one end, or aplurality of insulating members at opposite ends, of the electrodes. Inorder to overcome the formation of conductive paths on the insulatingspacing member, which, if present, prevent the electrodes fromperforming their proper function, a shield or baiile is positionedbetween the electrodes and the insulating member, the shield havingapertures of suitable diameter so that the supports from the electrodesmay freely pass through the baiile or shield without contactingtherewith and the insulating member engaging the supports to maintainthe electrodes in proper spaced relation.

In a specific aspect of the invention the insulating member comprises ablock having a central undercut portion and extending end projectionswhich engage a parallel baffle member to form a space between theinsulating member and the bafile member. The baflle or shield isprovided with slightly larger apertures thanthe insulating 'memberthrough which the electrode supports extend without coming in contactwith the baflie member and the supports extend into smaller apertures inthe insulating member which maintain the supports in proper spacedrelation. This arrangement substantially eliminates the formation ofconductive paths between the closely adjacent electrode supports sinceany conductive material thrown off the cathode will be deposited on thebaflie member. Therefore, the baflie or shield materially increases theoperating life of the device by preventing the formation of conductivepaths between the electrode supports which are directly in contact withthe insulating member or spacer.

Another feature of the invention relates to the support of theinsulating spacer or member adjacent the stem to prevent the depositionof conductive material on the insulator which aligns the severalelectrodes and also on the glass stem in which the leading-in wires forthe electrodes are embedded. In this arrangement a block insulator ispositioned between the parallel supports for the anode and is providedwith a cut out portion through which the cathode and grid extend, thecathode and grid being positioned ooaxially in the axis of the vessel. Alarge diameter circular baflie or shield extends across the cut outportion of the insulator, the baflle and insulator members being heldtogether by suspension hangers which extend therethrough and are joinedto the anode supports. The circular baflle member is also provided withapertures through which the electrode supports extend to the insulatormember without engaging the baffle member.

These and other features of the invention will be more clearlyunderstood from the following detailed description in connection withthe accompanying drawing.

Fig. 1 is a perspective view of one embodiment of the invention showinga discharge device with the enclosing vessel broken away to clearlyillustrate the electrode assembly;

Fig. 2 is an enlarged perspective view of the spacing insulator andbafile member adjacent the free ends of the electrodes, the grid andanode being removed from the supports to clearly illustrate theinvention; and

Fig. 3 is an enlarged perspective view of the insulator and baflieadjacent the stem, with the baffle member shown partially, in order toillustrate the details of the supporting structure for the insulator andbafile.

Referring to the drawing, the invention is disclosed as applied to athree-electrode equipotential discharge device as shown in Fig. 1 whichcomprises a highly evacuated enclosing vessel 10 having an inwardlyprojecting stem v of the insulator.

the press on the stem 11 and a bridging insulat- 1 ing member or spacer17, in the form of a rectangular block, which extends across the freeends of the rigid wires 15 and 16.

The insulating member 1'7 is provided with three aligned small diameterapertures in the central portion of the insulating block, the centeraperture providing a sliding fit for a pin support 18 which engages oneend of a cylindrical cathode 19 by pinching the cathode sleeve aroundthe wire as shown at 20, Fig. 2. "The cylindrical cathode is providedwith the usual coating of emissive material to insure a copious emissionof electrons to the other electrodes. A cylindrical insulator 21provided with twin bores is enclosed within the cylindrical cathode andserves as a spacer between the cathode and a helically wound hairpinheater element 22 located in the twin bores The outer apertures in theinsulating block 1'7 receive upright wires 23 and 24 supporting ahelical wire grid 25 which surrounds the cathode and is closely spacedtherefrom. The supports for the grid are rigidly positioned in theinsulating block 17 by anchor wires 26 which are seated in the block andare bent over and welded or otherwise secured to the grid supportingwires. One of the grid supporting wires 24 extends beyond the insulatingblock 17 and is attached to a flexible loop wire 27 which is sealedthrough the top of the enclosing vessel and attached to a terminal cap28. An anode 29 formed of two strips of metallic mesh cloth and shapedinto a cylinder having flanged portions: which engage the rigid uprightwires 15 and 16, surrounds the cathode and grid and serves as the outputelectrode of the [discharge device. A leading-in wire 29a is connectedto the rigid supporting wire 16 and one of the terminals 14 to enablethe connection of an operating potential on the anode.

An insulating block 30 is also supported beyond the stem of the vesselat the end of the electrodes opposite the block 17 and is provided, witha central aperture 31 through which the cylindrical cathode 19 extends,said aperture having a diameter slightly larger than the diameter of thecathode. Adjacent the cathode aperture 31 in the block 30 are twosmaller size apertures 32 which receive the grid upright wires 23 and 24to maintain uniform spacing between the cathode and the grid. Theapertures in the block 30 merely act as guides for the cathode and gridsince these electrodes are not held rigidly in the block 30. Thereforethese electrodes may expand longitudinally without afi'ecting therela'-,

tive spacing between the electrodes. The cylindrical cathode 19 isprovided with a tab 34 adjacent the stem, the tab being attached to aleading-in wire 35 which is connected to one of the terminals 14 on thebase 13. Two leading-in wires 36 and 37 are also provided in the pressand are connected to the terminations of the heater element 22 in orderto supply heating current to the heater to energize the cathode materialdeposited on the cathode.

Dueto the ads-"spacing ofthe electrode sup ports in the insulatingblocks at opposite ends of the electrodes and the large area of thecathode surface for emitting thermionically active -material in thespace between the electrodes, there is considerable danger of theemissive material from the cathode depositing on the insulating blockswhere it forms conductive paths between adjacent electrodes andeventually destroys the proper functioning of thedevice. In order toovercome this difliculty in accordance with this invention, a baflie orshield is interposed between the electrodes and the insulating members,the

bafile having apertures surrounding the electrode supports so that thesupports are out of physical contact with the baflle. The deposition ofactive material on the bafile will not affect the electrodes and willnot form conductive paths between the electrodes since the supports forthe electrodes extend through the baille without engagement therewithand the baflie prevents active material being deposited on theinsulating support in which the electrode supports are held.

The invention is disclosed in a three-electrode electron dischargedevice in which the insulating block or spacer 1'7 is provided with acentral undercut portion 38 in the region of the cathode and gridsupports. The plane surfaces of the insulating block 1'7 adjacent theundercut portion serve as bearing surfaces for a battle or shield 39,preferably of insulating material, such as mica, which may be ofapproximately the same size as the block 17 and is supported parallelthereto and rigidly affixed to the block 17 and the rigid upright wires15 and 16 by tie wires 40 and 41 respectively. These tie wires extendthrough similar size apertures in the block 17 and the baifle 39 and arebent outwardly above and below the block and bafiie and attached to therigid wires 15 and 16. The baiile 39 is provided with apertures throughwhich the electrode supports extend without engaging the baflie. Thisarrangement securely maintains the enlarged apertures in the bafliemember in alignment with the apertures in the spacing block 17 so thatthe supports for the electrodes freely pass through the baiiie withoutcontacting therewith. The undercut portion 38 of the insulating spacer17 forms a local area surrounding the closely spaced electrode supportsof the cathode and the grid to insure adequate insulation between theseelements. The bafile orv shield interposed between the electrodes andthe insulator prevents the deposition of active material from theoathode on the insulator where the electrode supports are held inposition. Any material thrown oil the cathode and deposited on thebafiie member does not affect the insulation between the electrodesupports, due to the free space surrounding each electrode support whichextends through the baiiie member. Therefore, even if conductivematerial deposited on the baflle member forms a conductive path thereon,this path will be discontinuous between the electrode supports and willnot cause any serious difiiculty with regard to the continued operationof the device. Due to the positioning of the baffle or shield betweenthe electrodes and the insulating member in which the electrode supportsare relatively fixed, the formation of conductive material on theinsulating member, should any of said material pass through the spacebetween the electrode supports and their corresponding openings in theshield, is limited to a substantially small area in the immediatevicinity of each support and will If ..i

not form a continuous path between adjacent supports.

The insulating block 30 aligns the cathode and grid in coaxial relationto the cylindrical anode and is also provided with a cut out portion 48in the central portion of the block in which are located apertures forreceiving the grid supports and cathode. A large diameter circularbaffle 42, of insulating material, such as mica, is placed over theblock 30 and is seated on the bearing surfaces of the block 30projecting on opposite sides of the undercut portion 48. The insulatingblock 30 and the large bafile 42 are maintained in relative position byU-shaped hangers or suspension members 43 and 44 which extend throughthe block 30 and bafile 42 with the free ends bent outwardly andembracing the rigid supporting wires 15 and 16, respectively. Thesuspension members 43 and 44 support the insulator and baflle as a unitwith the enlarged apertures in the baffle being held in alignment withthe apertures in the insulating block 30 so that the supporting wires ofthe grid and the cylindrical cathode extending through the insulatingblock 30 are free and clear of the bafile member 42. The bafile memberis also provided with enlarged apertures for the upright wires 15 and16. A feature of this construction is that the cathode and grid assemblymay be easily aligned in coaxial relation to the rigidly supported anodeand the central apertures for the electrode supports and the cathodeserves as a guiding member for the supports whereby these electrodes mayexpand longitudinally without distortion.

Another feature of the invention is the large diameter of the bafile orshield 42 which prevents the glass press receiving any deposit ofcathode material projected through the fine interstices of the meshanode 29. A getter support in the'form of a metallic cup 46 is supportedfrom the rigid wire 16 by a bent arm 47, the getter material beingvaporized in the final evacuation of the vessel to fix residual gases inthe device.

While the invention has been disclosed in a specific embodiment of adischarge device, it is of course understood, that various modificationsmay be made in the structure shown. Therefore,

the invention is intended to cover other types of devices in which adifiusible material may form a conductive deposit on a surface in whichelectrode supports are held, to prevent the conductive materialaffecting the operation of the device. Furthermore, while a specificembodiment of the particular baflle has been disclosed it is intendedthat the invention may take other forms and need not necessarily beformed of separate layers. Therefore, the invention includes allmodifications within the scope of the appended claims.

What is claimed is: I

1. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes supported beyond said stem, separatemeans for spacing said electrodes in operative relation, and meansinterposed between said electrodes and spacing means to prevent thedeposition of conducting material on said spacing means.

2. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes beyond said stem; supports for saidelectrodes extending from said stem,'a spacing member connecting saidsupports, and shielding means between said electrodes and spacing memberand free from engagement with at least one of said electrode supports.

3. An electron discharge device comprising an enclosing vessel having astem, electrodes spaced from'said stem, parallel supports extending fromsaid electrodes, double insulating members on at tending on the outersurfaces of said members engaging said supports, only one of saidmembers being in intimate contact'with said supports.

4. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes supported from said stem, an insulatingmember spacing said electrodes in operative relation, and a shieldcarried by said insulating member adjacent said electrodes, said shieldhaving portions free from contact with said electrodes.

5. A discharge device comprising an enclosing vessel having a stem,cooperating electrodes supported from said stem, individual projectionsextending from said electrodes, an insulating member extending acrosssaid electrodes engaging said projections to space said electrodes, anda baffle member between said insulating member and said electrodes, saidbaflle having apertures through which said projections extend withoutbeing in physical contact with said projections.

6. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes supported from said stern, projectionson said electrodes extending in parallel relation, and a combinationunitary bafile and insulating member extending across said electrodes,said insulating member having parallel portions and aligned aperturesthrough which said projections extend, said projections being in contactwith one of said portions and out of physical contact with said otherportion of said insulating member.

7. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes supported beyond said stem, a pluralityof insulating members positioned beyond the ends of said electrodes,supports between said electrodes and insulating members, and a bafllemember between each insulating member and said electrode ends, thesupports for certain of said electrodes being held in said insulatingmembers and freely passing through said bafile member.

8. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes supported beyond said stem, extensionson said electrodes, an insulating member extending across saidelectrodes and connecting said extensions, and a perforated bafileparallel to said insulating member and surrounding a plurality of saidelectrode extensions in a single plane without engaging said extensions.

9. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes beyond said stem, supports for saidelectrodes extending therefrom, a plurality of insulating memberspositioned beyond the ends of said electrodes and engaging saidsupports, and mica shields between the electrodes and said insulatingmembers, said shields having perforations sufliciently large so that theelectrode supports extend freely therethrough.

10. In an electron discharge device, a plurality of parallel supports,electrodes carried by said supports, an insulating member adjacent oneend of said electrodes connecting said support, a mica shield betweensaid insulating member and said electrodes, and tie members extendingthrough said insulating member and shield, said tie members engagingsaid supports.

least one end of said supports, and means ex- 1 1 11. An electrondischarge device comprising an enclosing vessel having a stem, aplurality of electrodes including a cathode, a helical grid surroundingsaid cathode, a cylindrical anode surrounding said cathode and grid,insulating members extending across opposite ends 01 said electrodes,supports for said cathode and grid extending through said members,supports for said anode extending from said stem to one of saidinsulating members, said other'insulating member being located betweensaid anode supports, a perforated shield adjacent one of said insulatingmembers through which said anode supports extend, and hanger memberssupporting said insulating member and associated shield from said anodesupports. i

12. An electron discharge device comprising an enclosing vessel having astem, a plurality of electrodes including a cylindrical cathode, ahelical grid closely surrounding said cathode, a cylindrical anodesurrounding said cathode and grid, in sulating members extending acrossopposite ends of said electrodes, supports for said cathode and gridextending through said insulating members, supports for said anodeextending from said stem to one of said insulating members, said otherinsulating member being located between said anode supports, aperforated shield adjacent one of said insulating members through whichsaid anode supports extend, and U-shaped suspension members extendingthrough said insulating member and shield, said suspension members beingbent outwardly between said shield and said electrodes and embracingsaid anode supports to prevent displacement of said shield. 4

13. An electron discharge device comprising an enclosing vessel having astem, a plurality of parallel rigid wires extending from said stem, acylindrical anode supported from said wires, a tubular cathode and ahelical grid coaxially positioned within said anode, an insulatingmember extending across said cathode, grid and anode remote from saidstem, said insulating member having a central undercut portion and planeend portions, an insulating strip engaging said plane portions, andmeans for holding said insulating member and strip together in rigidposition on said parallel wires, said undercut portion of saidinsulating member forming a local area between said'insulating memberand strip surrounding said cathode and grid, whereby substantially. noconducting material can accumulate to form a conductive path betweensaid cathode and grid.

14. An electron discharge device comprising an enclosing vessel having astem, a plurality of parallel rigid wires extending from said stem, aninsulating member extending across the free ends of said wires, acylindrical anode attached to said wires and interposed between saidinsulating member and stem, a cathode and grid coaxially positionedwithin said anode, said cathode and grid having extensions projectinginto said insulating member, a perforated baille carried by saidsupporting wires between said insulatingmember and electrodes, at secondinsulating member between said cathode, grid and anode and said stem, aperforated shield between said second insulating member and said anode,means for supporting said second insulating member and battle from saidrigid parallel wires, and a flexible wire beyond said first insulatingmember attached to said grid and extending to the exterior of saidvessel.

15. An electron discharge device comprising an enclosing vessel having aplurality of electrodes "including a cathode, an insulating member ateach end of said electrodes for holding said electrodes in spacedrelation, and a shield between each insulating member and the electrodesfor preventing the deposit of difiusible material from said cathode onthe insulating members.

ARTHUR H. DENZLER.

